One important focus area in E-UTRAN standardization work is to ensure that a new network is simple to deploy and cost efficient to operate. The vision is that new systems shall be self-organizing in as many aspects as possible.
In current wireless communication systems there are situations when a whole base station or part of the base station (e.g. a sector/cell of a sectorised base station) is in outage due to hardware/software failures.
When in outage the cell/base station cannot support any users in its vicinity and if these users cannot connect to another base station in the neighborhood then a coverage hole is created.
For the operators of wireless access networks this is undesirable consequence as potential revenue is missed from the unsupported traffic and also customer satisfaction is damaged.
A common practice today is that the wireless operators aim at repairing the malfunctioning cell/base stations as soon as possible (and therefore restoring the original coverage) without taking any compensation measures until the failure is repaired.
The goal of cell outage management is to minimize the network performance degradation when a cell is in outage through quick detection and compensation measures. The latter is done by automatic adjustment of network parameters in surrounding cells in order to meet the operator's performance requirements based on coverage and other quality indicators, e.g., throughput, to the largest possible extent.
Such network parameters may have an impact on the antenna configuration in terms of mechanical tilt (the antenna is rotated vertically), electrical tilt (the antenna max gain direction is rotated vertically by adjusting antenna element configuration inside the antenna), elevation (the combined effect from electrical and mechanical tilt), antenna lobe direction or azimuth (the antenna max gain is rotated horizontally), antenna lobe shape (the beam shape of the antenna, often characterized by horizontal and vertical beamwidths).
Altering the radio parameters of the neighboring cells means that some of the user equipments (UEs) served by those cells may be affected. This has to be taken into account as a coverage loss in the neighboring cells may not be tolerated.
Thus there is a need to address the problems with today's solutions, namely that coverage holes are not alleviated. This is an undesirable consequence as potential revenue is missed from the unsupported traffic and also customer satisfaction is damaged. This is particularly critical for services with a negotiated quality such as a guaranteed bit rate.
One previous attempt is disclosed in WO 2008030171, in which document is described a network reconfigurator for use in a telecommunications network comprising a network of radio base stations configured for providing radio access service to the telecommunications network for wireless stations. The network reconfigurator is arranged or configured, for differing service outages attributable to differing downed radio base stations of the network of radio base stations, to coordinately and dynamically change modifiable characteristics of plural remaining base stations for at least partially compensating for the service outages. Preferably the reconfigurator is configured, for differing service outages, to dynamically change differing modifiable characteristics of differing plural remaining base stations for at least partially compensating for the service outages. Modifying a characteristic of the plural remaining base stations can include modification of one or more of the following: antenna tilt of at least one of the plural remaining base station; power of a downlink common control channel of at least one of the plural remaining base stations; composition of a neighbor list of at least one of the plural remaining base stations; a parameter pertaining to one of handover, cell power, and cell size for the at least one of the plural remaining base stations.
A further document, US 2006/0084441 A1, describes how selected base stations are arranged to adjust the azimuth and elevation antenna radiation pattern of beams so as to reorient the beams to restore services previously provided by a disabled cell.
The document WO 2009/078764 also mentions that the coverage area, caused due to failure, can be altered by adjusting the position of one or more antennas.
One problem with the solutions suggested in accordance with the above mentioned documents is that coverage in neighboring cells may be lost when changing the antenna parameters.